Field
This invention relates generally to communication systems, and, more particularly, to wireless communication systems.
Description of the Related Art
A conventional communication system uses one or more access nodes to provide network connectivity to one or more mobile devices. The access nodes may be referred to as access points, access networks, base stations, base station routers, cells, femtocells, and the like. For example, in a cellular communication system that operates according to Universal Mobile Telecommunication Services (UMTS) standards, one or more access nodes may be used to provide wireless network connectivity to mobile devices. Mobile devices may include cellular telephones, personal data assistants, smart phones, laptop devices, text messaging devices, Global Positioning Systems, navigation systems, network interface cards, notebook computers, desktop computers, and the like and may also be call mobile subscribers or user equipment. Numerous types and generations of wireless communication systems have been developed and deployed to provide network connectivity for mobile devices. Exemplary wireless communication systems include systems that provide wireless connectivity to micro cells (e.g., systems that provide wireless connectivity according to the IEEE 802.11, IEEE 802.15, or Wi-Fi standards) and systems that provide wireless connectivity to macro cells (e.g., systems that operate according to the Third Generation Partnership Project standards—3GPP, 3GPP2—and/or systems operate according to the IEEE 802.16 and IEEE 802.20 standards). Multiple generations of these systems have been deployed including Second Generation (2G), Third Generation (3G), and Forth Generation (4G).
Wireless telecommunications networks provide mobile subscribers with the ability to access telecommunications services from almost anywhere in the world. Mobility management facilitates such world-wide access. With mobility management, wireless networks are able to track the locations of mobile devices so that mobile services can be delivered to the mobile devices.
A wireless network is typically formed of a number of cells, each coveting a small geographic area within which a mobile device may receive mobile services. A cell is typically equipped with a base station that provides radio coverage to the cell, thereby enabling communication with mobile devices located within the cell. By integrating the coverage of multiple base stations, a wireless network is able to provide radio coverage to mobile stations over large geographic areas.
The coverage area of a collection of neighboring base stations is commonly referred to as a location area. A location area is served by a Mobile Switching Center (MSC), and a MSC may serve multiple location areas. The MSC is the network node that provides circuit-switched calling, mobility management, and various other services (e.g., telecommunications services, mobile services, and the like) to mobile subscribers. The MSC maintains subscriber data for the mobile devices that are currently located within the location areas served by the MSC. Mobile subscriber data is permanently maintained in a Home Location Register (HLR) within the wireless network. When a mobile device is within the range of an MSC, the MSC acquires the mobile subscriber data from the HLR and maintains it in a Visiting Location Register (VLR) associated with the MSC. The location area of the mobile station is also maintained in the VLR associated with the MSC, for use by the MSC to page the mobile device in the location area when a Mobile Termination (MT) call is intended for the mobile device. The MSC that is associated with the current location area of a mobile station may be referred to as a Visiting Mobile Switching Center (VMSC) relative to the mobile station. The MSC receiving an MT call that is intended for the mobile subscriber may be referred to as a Gateway MSC (GMSC) for the mobile device. A combination of the MSC and the VLR for the MSC also may be referred to as an MSC/VLR.
When the mobile device on a cell has a Radio Resource (RR) connection, it also measures the signals of all neighboring cells and sends the measurement report to Base Station Controller/Radio Network Controller (BSC/RNC). Based on the signal strengths of the neighboring cells, BSC/RNC initiates a handover by sending HO/Relocation Required to the MSC. The mobile device does not move to the new cell until HO/Relocation Command is received.
When the mobile device on a cell is in the idle state, it measures the signals of all neighboring cells. The mobile device moves to the new cell (the neighboring cell with the strongest signal). Then the mobile device determines the location area identifier (LAI) changes by comparing the LAI of the new cell and the LAI stored in the mobile device. If the LAI changes, the mobile device sends Location Update message to the MSC.
During a call, Base Station Subsystem/Radio Network Controller (BSS/RNC) determines that a mobile device moves or “roams” from an old location area into a new location area and sends a handover required/relocation required message to the wireless core network (which requests that a handover procedure be performed). When the new VMSC serving the new location of the mobile device is different than the old VMSC serving the old location of the mobile device, an inter-MSC handover is performed as part of the handover procedure. In the context of the inter-MSC handover, “old” MSC means the “anchor” MSC; the “new” MSC means “target”/“serving” MSC.
When a call is not active and a mobile device roams, location updates are utilized to track the location and serving VMSC. For example, in a typical MT call scenario, an incoming call to the mobile station is first routed to a gateway mobile switching center (GMSC) of the called mobile station's HPLMN (Home Public Line Mobile Network). Upon receiving the call, the GMSC queries the HLR of the mobile subscriber to determine the VMSC on which the mobile station is currently registered. The HLR typically obtains routing information from the VMSC and returns it to the GMSC. The GMSC uses the routing information to route the call to the VMSC. The VMSC accesses its subscriber data for the called mobile subscriber to determine its location area and pages the mobile station within that location area to set-up a call connection between the caller and the mobile subscriber.
A mobile device can be identified by an International Mobile Station Equipment Identity (IMEI), a unique number assigned to the mobile device. A wireless network can utilize the IMEI to identify valid devices and provide other services. For instance, an MEI can be used to prevent a reported-stolen phone from accessing the network. The IMEI is only used for identifying the device and has no permanent or semi-permanent relation to the user of the device, who is identified by transmission of an International Mobile Subscriber Identify (IMSI) number.
Many network and security features are enabled by knowing the current mobile device being used by a subscriber. The mobile device may be identified by the IMEI or the IMEI Software Version (IMEISV), which include information on the origin, model, and serial number of the device. Examples of services that use IMEISV are Trace and User Equipment Specific Behaviour information (UESBI). In UESBI, the Core Network provides the Radio Access Network (RAN) with the IMEISV of the mobile device to enable the RAN to adapt its behaviour and the features it uses based on the characteristics (e.g., when the behaviour of a mobile device and the implementation of a feature in the RAN is known to not be fully compatible).